Easy-open composite container for packaging various products, particularly products under pressure such as refrigerated dough products and the like, constitute a significant commercial consumer product. These containers are usually formed of a spirally-wound paperboard or board stock bodywall layer, an interior or liner layer for preventing leakage of the contents from the container and an exterior label layer. The bodywall layer is wound in such a manner as to form a spiral easy-open seam extending from one end of the container to the other end of the container. When the outer label layer is either totally removed or that portion bridging the spiral seam of the bodywall layer is torn away from the spiral seam, the pressurized dough product expands outwardly and causes the spiral seam of the bodywall layer to open, in a manner well understood by those with ordinary skill in the art. This allows access to the dough and the interior of the container through the spiral easy-open seam in the container.
Various problems have been associated initiating easy-opening of the spiral seam so as to obtain access to the interior of the container. Many mechanism have been suggested to assist in the opening of the spiral seam. These include different constructions of tear strips associated with the easy-open spiral seam, selection of materials, placement of adhesives, etc. However, there still exists a need to improve the initiation and easy-opening of the spiral seam in these types of containers for pressurized food products and the like.
Accordingly, it is the object of this invention to provide a spirally-wound easy-open container for packaging various products, particularly products under pressure, and which provides an improved construction for easy-opening of the container and a method of manufacturing such container.
It has been found by this invention that this object may be accomplished by providing an easy-open container, and method of manufacturing same, particularly adapted for packaging products under pressure and which is spirally-wound and which includes a score cut opening panel therein for aiding in initiating opening of the easy-open spiral seam and which has the following components and features.
A paperboard bodywall layer in strip form is spirally-wound and defines a substantially cylindrical container having opposed ends. The bodywall layer has longitudinal edges lying adjacent each other and forming a butt joint or an overlapped skived edge joint to thereby define an easy-open spiral seam extending between the opposed ends of the container.
A flexible barrier liner layer in strip form is spirally-wound inside the bodywall layer in superimposed position therewith. The liner layer preferably includes an expandable joint comprising longitudinal edge portions overlapped with each other, an expandable fold formed by one of the liner layer edge portions being folded on itself and low strength bonding means positioned between the liner layer overlapped edge portions. The liner layer expandable joint is preferably positioned adjacent to and to one side of the easy-open spiral seam. High strength bonding means is preferably positioned between the liner layer and the bodywall layer except in the area between the liner layer expandable joint and slightly beyond the other side of the easy-open spiral seam from the liner layer expandable joint.
A flexible label layer in strip form is spirally-wound outside the bodywall layer in superimposed position therewith and has longitudinal edge portions overlapped with each other adjacent and to one side of the easy-open spiral seam. The uppermost of the label layer overlapped edge portions is positioned in bridging relation to the easy-open spiral seam. Preferably, this uppermost label layer overlapped edge portion is folded under on itself and high strength bonding means is positioned between the folds formed therein. High strength bonding means is also positioned between the label layer and the bodywall layer.
Tab cuts extend through this uppermost label layer edge portion and inwardly from an outer edge thereof past the spiral seam and through the bodywall layer longitudinal edge portion superimposed thereunder to define an easy-open pull tab including both the upper of the label layer edge portions and the inwardly underlying bodywall layer longitudinal edge portion. Score cuts extend through the bodywall layer and extend in diverging lines from the pull tab to define an easy-open panel for the container which is adapted to tear when the pull tab is pulled to easy-open the container.
The low strength bonding means described above preferably comprises a frangible adhesive and the high strength bonding means described above preferably comprises a permanent adhesive.
Thus, an easy-open container is formed which has a pull tab defined by tab cuts in both the superimposed label layer and bodywall layer extending inwardly from the overlapped longitudinal edges of the label layer for easy gripping when opening of the container is desired. This pull tab extends into a score cut opening panel in the bodywall layer which allows easy-opening of the container by opening-up a section of the bodywall layer when the panel is torn to expose the spiral seam and allow the pressurized food product in the container to expand and rupture the expandable joint in the liner layer to provide access to the user to the interior of the container.
While score cut panels have been utilized for opening of convolutely-wound containers, these convolutely-wound containers are less desirable for pressurized food products, such as biscuit and bread dough and the like, since they provide vertical or longitudinal bodywall edge seams which present poor graphic appearances and often allow wicking of moisture, etc. into or out of the container. These convolutely-wound containers usually require multiple convolute wraps or layers of the bodywall material to hold the container together and prevent premature opening. This also is not desirable from an economics standpoint. The use of such score cut easy-open panels for initiating opening of a spirally-wound container along an easy-open spiral seam has not heretofore been considered. Inherent problems are involved in forming cuts and score lines in bodywall layer strips being fed at acute angles for spiral-winding on a mandrel and to provide superimposed alignment of cut pull tabs in the bodywall layer and in the label layer. However, these problems have been overcome by the method of manufacture in the present invention by utilizing rotary dye cutting while controlling tension and feed of the various strips of material to the mandrel.